Telephone-exchange system.



M. L. JOHNSON.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED IuLY 15. 1912.

Patented'July 6, 1915.

4 SHEETS-SHEET l.

MORTON L JOHNSON AT TORNEY M. L. JOHNSON.

TELEPHONE EXCHANGE SYSTEM.

APPucATloN F|LED1uLY15.1912.

1,145,245. Patented July 6, 1915.

4 SHEETS-SHEET 2.

INV E NTOR. 4 MORTON L. OHNSON WITNESSES ATTORNEY NI. L. JOHNSON.

Patented July 6, 1915.

4 SHEETS-SHEET 3.

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Patented July 6, 1915.

4 SHEETS-SHEET 4.

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l 7@ r W n e y Y @www WITNEsEs INVENTR' um/ 771 .l @04o BYMORTONL JOHNSQN I.

'ATTORN EY NORTON L. JOHNSON, or onroaod ILLINOIS, AsSIeNon, 'BY MESNE ASSIGNMENTS, 'ro vrnaelvxn. COOK OOMI'ANY, or CHICAGO, ILLINOIS, a-OonronnTION or ILLINOIS.

rELnrHONn-EXOIIANGE SYSTEM.

Speciication of Letters4 Patent.

Patenten Jury eiais.

iillumination mamy/'15,1912 seriainmoaiai..

To fVzZZ whom it may concern .'V

Be it known that I,MoRToN L. JOHNSON,

' citizen ofthe United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Telephone-Exchange Systems-of'` which the following is a full.l clear, concise, andl exact description, referencebeinghad to the accompanying drawings, forming a partof this specification.

My invent-ion' relates to 'telephone ex` change systems and more particularly to that class .ofitelephone exchange systems in which lines;l extend totwo'boards of the exchange commonly'known' as A and B boards. By. means of myfnvention the A operators select the trunks tat `intervene between 'the' boards and inform the B operators of the selected trunks. vI employ selector switches, which may or may not'be individual to the trunlflines, for selectively associating the equipment 'at the operators positions at the B' board with the trunk lines that have been selected at the A board. The B operators may learn from the' A boardthenumber of the employed trunk line and the line that is to be called.v I have provided means whereby such information kmay be conveyed independently of the-telephone circuits and in this feature of my invention I employ means preferably individual to the trunk lines for creating characteristic signals and operator controlled means for telegraphically Sending signals respectively to lndicate the numbers of the employed trunk lines and the numbers of the 'lines that are to be called, Suitable signal receivers, which areprefe'rably signal recorders, being distributed among the various positions at the B board, the .selectors operatively associating these signal receivers with the trunk lines.

I will explain my invention more fully by reference to the accompanying drawings' showing the preferred embodiment thereof and in Which-f- Figure 1 is a view generally outlining the system of,my invention; and Figs. 2, 3 and 4, taken collectively, show more' in detail the l equipment illustrated in Fig. 1.

Referring first to Fig. l, IWill generally outline the novel features ofI my invention. The telephone lines extending from stations indicated at l are provided with springjack terminals '2 that are distributed among Operators positions at what may be termed the A board and which operators may be called A operators. .These lines are shown' as also extending to the operators positions at what maybe termed the B board 'Where B operators are located. The A and B boards may be in the same buildin@r or may be widely separated physically. Ihey form parts of ythe same telephone exchange system irreat the A board in the event' of the oonnections being established totally at the B board, though I do not limit myself to this arrangement. Iha've shown three operators positions C, D, E at the A board and three operators positions F, Gr and H atl-the B board. The usual cord circuits or link coin nectors 3 are provided at the operators positions C, D and Eat the A board for connecting the spring jacks 2 of -calling lines (calling line signalspi:l lines 1 and jacks@ being distributed among the operators positions at the A board) with spring ,jacks 4 of trunk lines `5 intervening between the A and B boards. The lines l extend to the B board and are there provided with multiple jacksl 6 at the various Sections' or operatorspositions of such board. The trunk lines are provided with multiple jacks 7 at the posi- Ations of the B board. Each B 4operator is jacks 7 at her position y l Hitherto the trunks 5 ended in plugs dis` tributed among the operators at the B board.`

I preferably modify the existing trunk line* 'i the operators positions of the B board 21mm employing the multiple trunk jacks 7 at the?" B Operators positions insteadof trunlrplugv equipment by extending the trunk lines'to.

terminals. Yl yslee piovicle loable Vlug; linl` connectors 8 st the B boei' cn secouiit of the substitution oi the tiene mls 7 1 place of tlie trunk plugs. when e l i tiatecl :it the A. boeifi, tlie'jecl 9;

ingliiie receiving?" epe/esteis posiz"` .l enel' s multiple jack ci s :tree tiuiil l' locetecl et suoli position, connectecl by cord circuit 3 et vsucli positione v l'lieii 10 selected B operatoi is meile acquainted 'with the iiunibei1 of. tbe 'tiunli conneceal' 'with tlie cord cii'cuit 3 at the A bcei enel tlie numbei' of the `olesiied line by ineens of the equip-- 'ment of my' invention te be ciesc'ibetl., tlie l5 selected B operator Will connect e cord cii'- cuit 8 Witlil tlie multiple jack tiene Hated trunk line sppee'fi'sg bei? posit-i and. the multiple jack of lesiiecl liiie also appearing at liei position. iistesil si? e 2G ploying oiclei' Wires between ii and boards l employ is-eens et the v il. '"i'ioziffc.l Wlieieby the i ope-remis op ete selecn tors 9, l@ anni Ills which ec b- 'being individuel to the 'trein z l 2,5 which individuel i'elatioiisliip tiie invention is not to be limited., tbeselselectoiis seivine; select signal receivers l2 tliet are loceteol theoperators positions enel which ere for selection and selectively to associate, the. signal receives with the tiuiiliiiies Wliicli the A operators have connected with ceiling; lines L The trunk lines 'are equipped W'itliY devices for' :crea-ting characteristic signals thst enable the trunk lines to (listinn guished et the B'boai'ol and the i'eceivers it Which are selectively associatedL with the trunk lines serve to -ieceive anni preferably to ,record the characteristic signals so that v lthe operators et the B boai'd` Will know the i0 trunks that the operators at the A board have selected. The opeietois :it the A boa-rel also desirebly opei'ete signal "receivers, which may be the semereceivers l2., so es to inform the operators at the B bosicl of the numbers of the lines desired by tlie calling` parties. The B operator hei/ing eeecnie Iquaintecl with the nunribei1 of the tiunl'liiie employed by the A opei'stoi' and having been informed of the nun'ibei of the clesiretl line proceeds to establish Connection between the automatically .designated trunk line and the desired line. The telephones 13 :incii of the and B operators may be employecl in place of the si'gnal receivers l2 to furnish the B operator with the number of the trunk Kline and the number of the 'desiiecl line, tlie B operators telephone 14C being' selecteii' as is the signal device l2, eacli signal device and each telephone constituting' c iesponsive device common to the'linll: connectors et the corresponding operators position. Thus a calling" station 1 has his line continued through his jack 2, a link connectoiL 3 at the A board, a trunk jack 4 of e `free trunk 5 s@ selected by the answci'ing A open-1:5013 t e 'tice f- "islly spese on. vi'liiclibeloii te tlie il. operator, s linie c "glie posi Ton oli' "tl e The ststion the .lp opei may b signalen :news signal f sippmetus assoc Wits employed-l cciiiiectoi" if? liie condictoi's Wliicl'i leed from opel-eters? sdelel clevices l2 the B ers teleplioiies'll in multiple cov with the Waiting; 'contacts of italics Q7 l() nl issyv siitcisiticjly' brise; 'the ti ster liste ceiinecticii ei itioii wien, tlie eej "i'pisientol u complete connections be usuel-z5 snel the les il l; line lies su teli sim' l5 ii Tete enel cciitscts'. i6 inolii l' 'is eleiiiients l5 indivi@ is UX'Jm unie line constituting ineens fer cingg :i characteristic signal at'tlie selec Lines iiiey estetici from-stations l? sis/ely to tlie l boiiicl Where' tliiey me? iiioviclecl with. mclti'pie jacks i8. 'l'.lie u oberstes link, cenni-actors 19 be ployefi iloi joining the stations?? with ell otliei" :incl with stations 'l when tliese la stations sie celleci..

Referring new to Figs., 2, Senti 4f, t tlesciiibe my invention inoie in cletsil. .lie. iigui'es, taken collectively, illustrate my sj tem and should be ei'anged in uumei oiolei with the conductors et the tops o' l e 'figures in slinement. Esch oit' the two stations l and each oiE vthe two substetio' l? :is provided with the usual tele-.pY equipment Wliicl. includes s telepl switch bool; 'liaving e normal Contact i establishing e bridge across the sicles of line that iiielncles signal bell 2l enti ce ieiisei' snol which switch liool; lies elteinete Contact for establishing eiiotliei ridge between the sifles ci its teleplic e tbet includes the telephone transini line 2 enti tlie telephone receiver 24. The sans 2 at the l boiled sie provided with tliinibles 25, tip line springs 26 and sleeve line spi-"ings 57. The common battery 28 be A bosiii.Il whose illustration is repeated for tlie sslise oi" clearness, is in normally open circuit :telstioii with e .line rele'y 29 of tlie'zissociste teleplione line. TWhen the telephone :cen ceivei' 2li is removed. et s calling station the two sicles of the calling line are me liciilly connected to establish circuit tlic the sssecieteline relay-whereby the line nel 30 individual to the line is opere'I4 Villen tbe .ioperetor answers by inseit the siis'weiingplug 3i oi s link cennectoi' f etliei icsit'isn circuit is esteblisliecl throng the cutolf relay 32 to restore the line signal 30. The answering A operator then depresses her listening key 33 to include her telephone set 34 in circuit with the calling line to ascertain the number of the line de- Isired. The operator inserts the connecting plug 35 that is companion to the employed answering plug 3l in` one of the trunk jacks '28 while the other terminals of these .wind- 'ings for a given trunk are in multiple con 4 that'bclongs to a free trunk line. When the link connector 3 is used for joining the calling line with a .trunk line the ringing current generator-36 is not employed, but a -signal transmitting vkey 37 may; be employed. for the' purpose of'tele'graphingto the B operator that. is selected, as hereinafter specilied, the number of vthe desired line, the number of the trunk line selected by the A operator being preferably vtelegraphed to the selected B operator. Instead olf telegraphin'g thesenumbers theA operator "may telephone the numbers to the selected B :operator by employing her tele hone set 34 and the trunk line which is then rought into telephonie lconnection with the selected -B operator. Each trunk line jack 4 at the A board is associated with a signal 38 individ ual'thereto for denoting the condition'of useof the associate trunk line. All of the 'signals 38 associated with each-trunk line are set into operation when anyvjackv4of" such line is connected with a link connector 3, oneterminal of each signal winding being grounded through the common 'battery nectioli with normally open contacts' 39 at .the contacts 39`where`by all of the signalsl 3 8 associated witha busy trunk *are dis'-' played to guard 'against the intrusion/upon ,such trunk by any other A operator. .Itwill not 'be necessary to' furnish further descripthe jacks 4. .When a plug is inserted in any `jack 4 at thev A board the grounded contact 40 at such jack is engaged with a'contact 39 sos to ground the multiple connection with tion of the Aboard equipment` illustrated .in Fig. 2 as the -various parts and circuit arrangement shown and not specifically described will be readily understood' by those skilled in the' art. l

rigs, 2 to 4, inclusive, show two `trunk lines each having B operator selecting aparatus individual thereto, as the invention 1s illustrated, but to which arrangement the invention is not lto be limited. When a trunk jackl 4 is plugged into; at the A board a circuit is established which may be traced 'from the grounded connection 41 at the A board 'through' the repeating coil 42, the tip of the connecting plug 35, the tip. 'spring of the jack 4 engaged by said'plug, relay 43 through grounded battery which may be the common battery '28.' The relay4 43 is energized to establish circuit.' which `may be traced from the grounded." armature switch I 44, the right hand armature switch of relay 43, armature switch of the sluggishly operating interrupter relay 45, the rotary magnet 46, the side switch wiper 47 (in its lirst position) 4to the grounded battery 28. On the initial operation of the rotary magnet 46 circuit is established forthe private magnet 47 4which circuit is maintained as long as the wiper 48 encounters grounded contacts 4-9. When an ungroun'ded contact 49 is found the private magnet 47 is de energized and the side switch wipersr 47,

50 and 51 are placed in second positions. When this occurs the rotary magnet is deenergized at 47 so that the wipers 48, 52, 53 and 54 are arrested. The. relay 55 is now energized through the side switch wiper 47,

the right hand armature switch of the en-v i ergized relay 43 and the left handarmature switch of the inert magnet 56. The armature switches ofrelay' 55 are now moved to connect wipers 52 and 53 with the talking sides. of the trunk that was selected by the A operator and these wipers 52 and 53 are in connectionwith conductors 57 and sition where these'conductors may be connected with the selected *B operators televphone 59 by means of a key 60 at such posi- -inagnet 6 8,n this releasedmagnet circuit being now .opened at' the'lower armature switch of relay 61; The shaft of the wheel 66 carriesthe lswitch arm 63 and another switch arm 69, the movement of the wheel 66 occurring as long as the arm 63` engages the contact `62. Whencontacts 62 and 63 are separated the magnet 6 4 is in open circuitcausing the'wheel 66 to rest. The switch arm 69 passes over telcgraphing contacts 70 which 'are intermittently included by the arm 69 in a circuit whichmay be traced from these contacts which4 are groundedy through the wiper 54, the contact then engaging the same, the relay 72, to the grounded battery which maybe the common battery 28'. l The relay 72 is intermittently operated tocause the signal receiver 12'to print the number of the trunk line with whichrthe signal receiver 12 has become selectively associated. After the number -of the ltrunk line has been` recorded at 124the A operator supervising the connection will cause the securingof'the 90l 58 that lead to the selected B operators pof ce called line 'at 12 by way or" thecircuit which isv traceabierom the grounded contact voli key 37, the heel 'of the plug 35, the thirnble of the jack engaged by said plug, the conductor 73, ythe contact 74 finally engaged by the armvGQ, said arm, the Wiper 54, the relay 72 and the grounded battery 28. The se lected B operator either in response to the requirements furnished to her by her telephone 59er by Aher signa-l receiver l2, inserts the plug 75 of one of her link connectors 8 into the multiple jack corresponding to the designated trunk 5 and inserts the mate 7o of such pluga into the jaclr 6 (or the jack 13) belonging to the wanted line. Plug Z5 when thus inserted in trunk jack 7', operates to release the actuated automatic selector switch that brought the trunkline selected by the operator into its associa,- Ation with an idle D operator, a circuit ,being established which is traced from the grounded battery 23 through the heel et the plug 75, thirnble or". the jack 7, the windingof relay 56, 'to ground. 'Circuit for 'relay is thejnopen'ed so that its armatures are restored 'to normal. The left hand armature i switch of relay 43 then establishes a circuit Athrough the release magnet 63 to cause the spring 79 `to restore the wheel 66 and wipers 63 and69 to normal, the release circuit being opened at 67 when the wheel 66 reaches normal. The signals 38 oi the employed trunk line remain displayed until the plug 75 is withdrawn at the selected B operators position owing to the connection established between the left hand armature switch of' relay 56 and its alternate contact. r`he sun pervisory signaling apparatus eplied for the link connectors 3 and 8 is in accordance with well established telephone practice.

,The two selector switches shown in detail in Fig.v 3 are 'of similar construction and similar parts are supplied with similar char acters of reference. The waiting contacts of the wipers 48, 52, 53 and 54 of the difierent switches are respectively multiplied. Each operators conductors 57, 58 leading to her telephone and each conductor leading to her relay 72 is provided with a waiting con tactupon each switch, there being as many sets of vsuch. waiting. contacts .as there are operators positions. Seekingl switches are prevented `from engaging waiting contacts of previously appropriated conductors 57, 58 by means of a ground established by the A these buttons being inultipled, suc

. nectors'at the boards for connecting); the te ;A

`free to be selected with the trunk vistie signals by said signal receivers 'to nate the trunk lines selected said et side switch. wiper 5G in second per ground being connected byway oi 48 with the button 4:9, each switch such a button individual to eachv :B

maintaining the circuit of private L17. as previously eXpl ined. The 'eolien at the upper part of' 3 dirigere `fro equipment at the lower part in that the c tacts 50 associated withthe switches-'ar.` tinguished so as to lconvey character stic s nals to the receivers l2 when seiectiv j sociated therewith.

lit is not thought necessary the mechanicalv construction inatic switches. Materiai o find counter, parts in. the shown upon page et Yan Telcpionology, pubiisherl in 'A 'vertical magnets and the nieve eii'ect being omitted.. The y struction is further ex'ernpdv to iritish iatent i293 of 19;

En my cri-pending application 709,423 -and 709,429, Filed oi even with l have `disclosed means for. registerthe numbers of calling lines in of receiving operators and selecta nism for setting up the digits et' in the presence of receiving operato While have herein shown and -A larly described the preferred my invention it is obvious that chl readily he madel without departing spirit thereof and lf. do not therefore be limited to the precise details et conm tion and circuit arrangement' shown,

Having rthus described ini/enti'in claim as new and desire to secure by Lett Patent the following?u y f l. A telephone exchange system includ ing lines extending from telephone st to different boardsv of an exchange; lines intervening between these boards;

phone lines with the trunk lines ane there. with each other; operators signai rec located at different operators positi one of the boards; selector switches ciated. with the trunk lines for selecti associating Vsaid signal receiwiers tlc means at the other board associated trunk lines for setting,t said selector s in operation; and means, controiled other board, and individual to the lines for creating` difierentiating"ch:v

board. I

2. A telephone exchange system ing lines extending trointelephone sta to different boards'ot an exchange; lines intervening; between these boaerlsfy coa nectors at the boards tor connecting teiephone lines with the trunk lines and 'thereby I with leach other; operatorsrecording signaldevices located at different operators posiltions at one of. the boards; selector switches associated' with the trunk lines for selec'- tively associatingl said operators recording signal-devices that are. free to be selectedwith the trunk lines; means at the other board associated with the trunk lines for setting said selector switches in operation; and means, controlled at the other board, in-

dividual to the trunk lines for creating dif-l erentiating characteristic signals by's aid recording signal devices to denote the trunk lines selected at said other board..

3. A telephone exchange system including lines extending from telephone stations to are freel to different boards of an exchange; trunk lines intervening between these boards; connecltors at the boards for connecting the Itelephone lines with the trunk lines and thereby with each other; operators signal receivers located at different operators positions latone of the boards; selector switches associated with the trunk lines for selectively associating said signal receivers that means at the other board associated with the trunk lines for setting said selector switches in operation; and means controlled at the other board, and operatively associatedwiththe trunk lines for creating differentiating" characteristic signals by -said signal receivers to designate the trunk lines thereby selected 'at said other board.

4. A telephone exchange system including lines extending from telephone'y stations to diiierent boards of an exchange; trunk lines intervening between these boards; connectors at 4the boards for connecting the telephone lines with the trunk lines and with each other; operators re' associated with the trunk. lines for creating diderentiating characteristic signals by said -recording signal devices to denote the trunk i vlines selected at said other board. v

5. A telephone exchange system includ--y 'ing lines extending from telephone stations to different boards of an exchange; trunk lines intervening between these boards; connectors, at the boards for connecting the telephone lines with the trunk lines and lthereby with each other; operators signal receivers' located at different operators positions' at Aone of .the boards; selector switches be selected with trunk lines;'

associated with the trunk lines for selectively associating said signal receiversthat are tree, to be selected with vtrunk lines; means at the other board associated with the trunk lines for ysetting said selector switches in operation; and means controlled. atthe other board for creating diiierentiating characteristic signalsby. said signal receivers to designate the trunk lines selectedI at saidA other board. n 6. A telephone exchange system including lines extending from telephone stations to diferent boards of an exchange; trunk lines intervening between these boards; connectors at the boards for.' connecting the telephone lines with the trunk lines and thereby with each other; operators recording signal devices located at diierent operators positions at one of the boards; selector switches associated with the trunk lines for selectively associating said operators recording signal deviceswth'at'arefree to be selected with the trunk lines; means at the otherboa'rd associated with the ltrunljr lines for setting said selector switches in opera-j tion; and means, controlled at the. other board, for creating differentiating characn 7 telephone exchange system including lines extending from telephone stations t0 different boards of anexchange; trunk teristic signals by said recording signal de-l l vices to denote the trunk lines selected at.

' said other board. 95

lines intervening between these boards ,cona nectors at the Yboards for connecting the telephone lines with the trunk lines and thereby with' each other; operators signal receivers located at diiierent operators positions at one of the boards, at which positions the telephone lines and trunk lines are provided with multipled terminals employed in es-` tablishing connections there between. the telephone lines andthe trunk lines; selector switches associated with the trunk lines-for selectively associating said signal receivers that are free to be selected with the trunk lines; means at the other boardf associated with the trunk lines for setting said selector switches. in operation; and means, controlled' at the other board, and individual 4to the trunk lines for creating differentiating characteristic signals by said signal receivers to iis designate the trunk lines selected, at said other board.

' 8. A telephone exchange system including 4lines extending from telephone stations to' different boards oan exchange; trunk lines intervenlng between these boards; connectors'at the boards for connecting the'tele-l v phone lines with the trunk lines and thereby with each other; operators recording signal devices located at different operatorsv positions at oneof the boards, at whichpovsitions the telephone lines and trunk lines are provided 'with multipled terminals ernone of the boards; and means controlled at-l the other board and individua-l to the trunk to diierent boards of-an exchange; trunk v lines intervening between these boards; connectors for connecting the telephone-"lines with the trunk lines and thereby with each other;l an operators signal receiver common to the trunk lines and located at an operators position at one of the boards; and

` meanscontrolled at the other board and individual to the ,trunk lines for creating diferentiating characteristic signals by lsaid signal receiver to designate the trunk lines selected at said other board.

16. A telephone `lexchange system including lines extending from telephone stations vto diil'erent. boards of an exchange; trank linesvintervening between these boards; connectors for .connecting the telephonelines with the trunk lines and thereby with each other; an operators recording signal receiverlocatedatan operators position at` lines lfor creating diierentiating character- Y isticsignals by said signal receiver to designate the trunk lines selected at said other board. A

. y17. A telephone exchange system including lines ext nding from telephone ,stations to different cards of an exchange; trunk lines intervening between these boards; connectors for connecting the telephone lines with the trunk lines'and thereby with. each other; operators signalreceivers .common to the trunk lines and located at different operators positions at'one of the boards; and means controlled at the other board for creating differentiating characteristic signals by said signal receivers to designate the trunk lines selected at said other board. 18. A telephone exchange system including lines extending. from telephone stations to different boards of an exchange; vtrunk lines intervening between these boards; connectors for connecting the telephone lines with the .trunk lines and thereby with each other; operators. recording signalreceivers located at different operators positions at one of the boards; and means controlled at the other board for creating differentiating characteristic signals by said signal receivers to designate lthe trunk lines selected at said: other'board. y. i 19. A telephone exchange system includv inglines extending from telephone stations to different boards of an" exchange; trunk lines intervening between these boards; connectors for connecting the telephone lines with the trunk lines and thereby with each aaa other; an operators signal receiver. common to the trunk lines and located at an" operators position latone of the boards; and means controll d at the other -board f or creating ldifferentiating characteristic signails by said'signal receiver to designate the.

trunk lines-selected at said other board.

, 20.Atelephone exchange system including lines 'extending from telephone stations to different b oaids of an exchange; trunk lines intervening between these boards; con- -nectors for connecting the telephone lines with the trunk lines and thereby with each other; an operators lrecording signal receiver located at an operators position at one of the boards; and means controlled at .the other -board for creating differentiating characteristic signals by said. signal receiver to designate the trunk lines selected'` at said other board.

21. A telephone exchange lsystem includ-` ing lines extending from tele-phone stations tordiier/eI- itv boards of an exchange; trunk lines* intervening between these boards; connectors for connecting the telephone lines a with the trunk lines and-thereby with each other; operators signal-.receivers located'at -diierent operators positions at one' of the boards; selector switching mechanism forl interchangeably associating idle 'signal ref ceivers with the trunk lines; and means controlled at the .other board and individual to the trunk lines for creating 'diierentiating characteristic signals by sasid 'signal' re- 'ceivers to designate the trunk lines selected at vsaid other board.

22. A telephone exchange system including lines `extending from telephone stations to different boards of an exchange; trunk linesintervening between these boa-rds; connectors for connecting the telephone lines with the trunk lines and thereby with-each other; operators recording signal receivers located at'diierent. operators positions at lone of the boards; .selector switching mechanism Afor interchangeablyl associating idle i signal receivers with the' trunk lines; and

means controlled at the other board vand 1ndividual to the trunk lines for creating differenjiiating haracteristic signals lby said signal receivers to designate the' trunk lines selected at said other board.

23. A telephone exchange system including lines extendingl from telephone stations to different boards of an exchange; trunk lines intervening between these boards; connectors for: connecting the telephone lines with the'trunk lines and thereby with each other; an operators signal receiver located at an operators position at one of the boards; selector switching mechanism for interchangeably associating an 'idle vsignal receiver with the trunk lines; and means controlled at "the other boardaiid individual to the trunk lines for creating differentiater to designatejj the trunk lines selected other boardi ,lines extending from telephone stations beards of an exchange; trunlr es intervening between these boards; con- "for connectingv the telephone lines Airiinl lines and thereby` With each 1i? other; an4 operators recording signal receiver located at an operators position 'at one of the beards; selectorA switching mechanisin for interchangeably associating an idle signal. receiver with the trunklin'es; and l5 iiieans controlled at the other b oardand indiwidiial to the trunk lines lfor creating difreniiatiiig -Y characteristic' signals by said l receiver to designate the trunk li'nes ctcd ether board. I te eplione exchange system includerent boards of" anexchange; trunk A ,ening between these boards; con- ;rci" connecting'l the telephone lines i ce trifinlriines and thereby with each c eters signal receivers located epcrators positions at one of the l lector switching mechanism for .foly associating idle signal re i the trunk lines; and means coiithe eti/ier board or'creating dii!- 'iatin'g cha. acteristicsignais by said receivers te designate the trunk lines ed a said other hoardi one exchange system includfi'oin telephone stations ent boards' an' exchange; trunk connecting the telephone lines `I`e tiiinli lines and therebyv with each 'fepi-cratersj recording signal receivers ccm-ed diliei'cnt.I'operators nositionsat ene ci the bcards;selector switching naechifi .telephone exchange system includ lines ente-aiding from telephone stations,

1i. -rifening between-these boards; coni aiiaeee vinterchangeably associating an idle signalv receiver With the trunk lines; and ineens cc controlled at the other board forfcreating differentiating characteristic signals by said signa-l receiver to designate the trunk selected at said otherboard.

28; A telephone exchange' systeniincl ing lines extending frein telephone stati to different boards of an exchange; tri" lines intervening between these boards; coi nectors for connecting-the telephone lin With the trunk lines and thereby With-- other; an operators recording signal il; oei located at an operators position one of the boards; selector switching` ine anisinfor interchangeably associatir idle sien-al receiver with the trunk li and inc-ans controlled the other beard creating diierentiating characteristic nais bysaid signal receiver to designate trunklines selected at said other board,

ln Witnesswliereof, hereiinto subscribe 35E my name this third day or July A. D., lli-lli,

7Wi tnesses G. L. Cease, Er'rii L. ilVi-iirn.

Vasliington, D. G. 

